Micro-Level and Macro-Level Flow Mechanics of Wet Granular Media

湿颗粒介质的微观和宏观流动力学

• 批准号: 0411634
• 负责人: Christine Hrenya
• 金额: --
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-03-01 至 2008-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0411634&HistoricalAwards=false
• 关键词: Micro; Level; Macro; Flow; Mechanics

ABSTRACT - 0411634Intellectual Merit. Processes involving the flow of solid particles are ubiquitous in bothnature (landslides, planetary rings, etc.) and industry (pharmaceuticals, food products, chemical process industries), though a predictive understanding of their behavior remains an elusive goal. Of particular interest in the proposed effort are systems involving particles coated with a thin layer of viscous fluid - i.e., wet solids. Such particulate systems are found in a wide range of applications, including fluidized-bed granulation, mixing of pharmaceuticals, pollen transport, filtration, etc. Such systems are known to display characteristics that are typically not exhibited by their dry counterparts, namely the presence of particle agglomerates. A predictive knowledge of agglomeration formation, rearrangement, growth, and break-up is a key element in the rational design of wet-solid processes, though such a predictive tool is not currently available. The current effort aims to address the aforementioned need, with a particular focus on viscous (dynamic) effects occurring between wetted particles, which are relatively unexplored as compared to the capillary (static) effects of wetted systems and viscous effects of fully-immersed systems. A combination of theory, experiments, and discrete-particle simulations will be used to answer the following critical questions associated with wet solids: (i) Will an agglomerate form when two "free" particles collide? (ii) If an agglomerate is not formed, what is the impact of the liquid layer on the post-collisional particle motion? (iii) If an agglomerate does form, what is the result of a collision with a third particle? (iv) How do these micro-level physics impact the macro-level (continuum) behavior of both granular and gas-solid systems? More specifically, a combination of experiments and fundamental theory based on lubrication, capillary forces, and solid mechanics will be used to develop stick/bounce and breakup criteria for small agglomerates. The theory will require only measurable solid and liquid properties for solution. To bridge this micro-level physics with macro-level behavior, the microphysical theory will be incorporated into discrete-particle simulations. The effect of the liquid layer on continuum quantities like stress will be assessed via an examination of simple shear flow of a granular material. Furthermore, discrete-particle simulations will also be carried out for a specific gassolid operation, namely fluidized-bed granulation (or enlargement), in an effort to describe some non-intuitive behavior observed in such systems. This work will be a collaboration between the PI (Prof. Christine Hrenya) and the co-PI (Prof. Rob Davis), who have extensive background in the theoretical, experimental, and simulation aspects associated with particulate flows.Broader Impacts. The broader impacts of the work include the following: (i) a morefundamental understanding of wetted particulate system, (ii) training of graduate students in the area of particle technology, which has been identified as a national need [1-3], and (iii) sharing of learned information with both the technical community (via presentations and peer-reveiwed publications) and the student community (via incorporation into coursework, training programs, and outreach).

摘要-0411634Intlectual功绩。涉及固体颗粒流动的过程在大部分（滑坡，行星环等）和工业（药品，食品，化学过程行业）中无处不在，尽管对其行为的预测性了解仍然是一个难以捉摸的目标。 在提出的工作中特别感兴趣的是涉及涂有薄粘液液层的颗粒 - 即湿固体。在广泛的应用中发现了此类颗粒系统，包括流化的床颗粒，药物的混合，花粉运输，过滤等。已知这些系统表现出这些特征，这些特征通常不会由干燥的对应物显示出来，即存在粒子团聚。关于聚集，重排，生长和分裂的预测知识是湿固过程合理设计的关键要素，尽管目前尚不可用这样的预测工具。 目前的努力旨在满足上述需求，特别关注湿粒子之间发生的粘性（动态）效应，与湿系统的毛细管（静态）效应相比，这些颗粒相对尚未探索，并且完全不受欢迎的系统的粘性效应。理论，实验和离散粒子模拟的结合将用于回答与湿固体相关的以下关键问题：（i）当两个“自由”粒子碰撞时，会形成一个团聚形的形式吗？ （ii）如果未形成团聚，液体层对后粒子运动的影响是什么？ （iii）如果团聚形成，则与第三粒子发生碰撞的结果是什么？ （iv）这些微观物理学如何影响颗粒和气体固体系统的宏观（连续性）行为？更具体地说，基于润滑，毛细作用力和固体力学的实验和基本理论的组合将用于制定小凝集剂的棍棒/弹跳和破裂标准。该理论将仅需要可测量的固体和液体特性才能解决方案。 为了用宏观行为桥接这种微观物理学，将将微物理理论纳入离散粒子模拟中。液体层对诸如应力之类的连续量的影响将通过检查颗粒材料的简单剪切流程进行评估。此外，还将进行离散的粒子模拟，以进行特定的Gassolid操作，即流化的床颗粒（或增大），以描述在此类系统中观察到的某些非直觉行为。 这项工作将是PI（Christine Hrenya教授）与Co-Pi（Rob Davis教授）之间的合作，他们在与颗粒流相关的理论，实验和模拟方面具有广泛的背景。这项工作的更广泛影响包括以下内容：（i）对湿润颗粒系统的更多了解，（ii）对粒子技术领域的研究生的培训，这已被确定为国家需求[1-3]和（iii）与技术界（通过演示和同行雷夫德出版物）和学生社区（通过将课程，培训计划和外展纳入学生社区）共享学习的信息。